A CFD solution of oil spill problems

Journal of Applied Mathematics, 2012

The spreading of oil in an open ocean may cause serious damage to a marine environmental system. Thus, an accurate prediction of oil spill is very important to minimize coastal damage due to unexpected oil spill accident. The movement of oil may be represented with a numerical model that solves an advection-diffusion-reaction equation with a proper numerical scheme. In this study, the spilled oil dispersion model has been established in consideration of tide and tidal currents simultaneously. The velocity components in the advection-diffusion-reaction equation are obtained from the shallow-water equations. The accuracy of the model is verified by applying it to a simple but significant problem. The results produced by the model agree with corresponding analytical solutions and field-observed data. The model is then applied to predict the spreading of an oil spill in a real coastal environment.

Journal of Marine Science and Engineering

Several oil spill simulation models exist in the literature, which are used worldwide to simulate the evolution of an oil slick created from marine traffic, petroleum production, or other sources. These models may range from simple parametric calculations to advanced, new-generation, operational, three-dimensional numerical models, coupled to meteorological, hydrodynamic, and wave models, forecasting in high-resolution and with high precision the transport and fate of oil. This study presents a review of the transport and oil weathering processes and their parameterization and critically examines eighteen state-of-the-art oil spill models in terms of their capacity (a) to simulate these processes, (b) to consider oil released from surface or submerged sources, (c) to assimilate real-time field data for model initiation and forcing, and (d) to assess uncertainty in the produced predictions. Based on our review, the most common oil weathering processes involved are spreading, advectio...

2013

An oil spill model coupled with a hydrodynamic model was developed to simulate the spread of oil slick in real marine conditions considering the effects of tidal currents, wind and wave. The hydrodynamic model is verified using the measurements of tidal elevations and current speeds at the Persian Gulf. Effect of various governing factors on oil slick movement, tidal currents, wind and wave, are examined. It is concluded that the wind action is the predominant factor for the spreading of oil while the overlaying waves are the second important driving force. Although the tidal currents spread the oil slick on a wider area, they have limited influences on the net transformation of slick. The performance of the model on a field data in the Persian Gulf shows that the present model is capable to predict the spread of oil in early days of the oil spill.

2010

The environmental concern over marine oil spills has lead to the development of mathematical models that simulate the transport and fate of oil slicks. These models are used for spill response during accidents, environmental impact assessment, contingency planning, and response training. Spilled oil is transported, and its composition and character altered by a variety of physical, chemical, and biological processes. This paper presents a mass balanced oil spill transport model that uses hydrodynamic results obtained with a one-dimensional Crank-Nicolson numerical scheme to predict the mass concentration of spilled oil in time and space.

Ocean Engineering, 2008

This study extends previous two-dimensional research . Two-dimensional numerical simulation for transport and fate of oil spills in seas. Ocean Engineering 32, 1556-1571] to three dimensions in order to investigate the vertical dispersion/motion of the spilled oil slick, which is a more realistic model of the motion of the spilled oil. To this end, a threedimensional (3-D) model, based on the particle approach, is developed for simulating oil spill transport and fate in seas. The amount of oil released at sea is distributed among a large number of particles tracked individually. These particles are driven by a combination of water current, wave-and wind-induced speed and move in a 3-D space. Horizontal and vertical diffusion are taken into account using a random walk technique. The model simulates the most significant processes which affect the motion of oil particles, such as advection, surface spreading, evaporation, dissolution, emulsification, turbulent diffusion, the interaction of the oil particles with the shoreline, sedimentation and the temporal variations of oil viscosity, density and surface tension. In addition, the processes of hydrolysis, photooxidation and biodegradation are also considered in this model. The model has been applied to simulate the oil spill accident in the Bohai Sea. r

Advances in Difference Equations, 2019

An oil spill is the release of liquid petroleum into the marine ecosystem leading to huge damages in the natural resources. Prediction of oil spill spreading can help in handling accidental oil spills. This study is to present numerical simulation to predict the movement of oil slicks in the Gulf of Thailand, based on the wind speed prediction obtained by an ocean wave model. The numerical results show that oil slicks can move toward different coastal areas.

Modelling and Simulation in Engineering, 2012

The world production of crude oil is about 3 billion tons per year. The overall objective of the model in present study is supporting the decision makers in planning and conducting preventive and emergency interventions. The conservative equation for the slick dynamics was derived from layer-averaged Navier-Stokes (LNS) equations, averaged over the slick thickness. Eulerian approach is applied across the model, based on nonlinear shallow water Reynolds-averaged Navier-Stokes (RANS) equations. Depth-integrated standard k-ε turbulence schemes have been included in the model. Wetting and drying fronts of intertidal zone and moving boundary are treated within the numerical model. A highly accurate algorithm based on a fourth-degree accurate shape function has been used through an alternating-direction implicit (ADI) scheme which separates the operators into locally one-dimensional (LOD) components. The solution has been achieved by the application of KPENTA algorithm for the set of the flow equations which constitutes a pentadiagonal matrix. Hydrodynamic model was validated for a channel with a sudden expansion in width. For validation of oil spill model, predicted results are compared with experimental data from a physical modeling of oil spill in a laboratory wave basin under controlled conditions.

Spill Science & Technology Bulletin, 1995

A numerical model for the simulation of tbe physicocbemical weathering processes of an oil spill at sea is presented based on state-of-the-art models. The model includes the most significant processes: spreading, evaporation, dispersion into the water column, emulsification and the change in viscosity and density. These processes depend on each other and are allowed to vary simultaneously since processes are described by a set of differential equations, solved by a fourth-order Rung+Kutta method. Numerical examples are given, in order to test the results obtained, and compared with available experimental data in tbe literature. The model predicts well the variation of water incorporation, density and viscosity but seems to overestimate the fraction evaporated. However more experimental data are needed to calibrate and validate the model since differences in the composition of the simulated oil and the samples from which experimental data are taken may occur in evaporation studies. The model is suitable to join other modules for the prediction of the spill trajectory by advection due to winds and currents and sub-sea transport.

Journal of Hydraulic Research, 2003

A multiphase oil spill model has been developed to simulate consequences of accidental oil spills in the marine environment. Six state variables are computed simultaneously: an oil slick thickness on the water surface; concentration of dissolved, emulsified and particulate oil phases in the water column; and concentration of dissolved and particulate oil phases in the bottom sediments. A consistent Eulerian approach is applied across the model, the oil slick thickness is computed using the layer-averaged Navier-Stokes equations, and for transport of the oil phases in the water column the advection-diffusion equation is employed. The kinetic terms are developed to control the oil mass exchange between the variables. The governing equations are verified using test cases, data and other models. The model is useful for short and long-term predictions of the spilled oil dynamics and fate, including application of the oil combating elements, such as chemical dispersants and booms.

2015

This paper presents the results of oil spill simulation in the northwest of the Persian Gulf, next to Al-Ahmadi oil wells. A two-dimensional depth averaged flow and oil pollution model is developed for coastal water simulation. To increase accuracy advective terms in transport equation were discretized by applying third-order upwind scheme and modified by using GH limiter. The oil spill is considered in two different layers: surface smudge layer and depth emulsion part. The model takes into account the major physiochemical phenomena of oil spill including wind and current speed, oil evaporation, dissolution and coastline deposition. Average monthly wind speed has been used for long-term prediction in the Persian Gulf. Comparing the model result with the actual measured data in the incident sight revealed good agreement for predicting oil spill behavior and model accuracy.

Water Pollution XI, 2012

The application of the European Water Framework Directive and the monitoring obligation on water quality for human consumption and industrial activities create a need for water quality evaluation and monitoring systems. The Migr'Hycar research project was initiated to provide decisional tools, and fulfil operational needs, for risks connected to oil spill drifts in continental waters. Within the framework of the Migr'Hycar project, a new 2-D numerical oil spill model has been developed by combining Lagrangian and Eulerian methods. The Lagrangian model describes the transport of an oil spill near the surface. This model simulates the major processes acting on the spilled oil. Though generally considered as a minor process, dissolution is important from the point of view of toxicity. To model dissolved oil in water, a Eulerian advectiondiffusion model is used. The fraction of dissolved oil is represented by a passive Eulerian scalar and its quantity directly depends on the dissolved mass of particles. In parallel with model development, experiments on the behaviour of hydrocarbons have been carried out in an artificial river facility in Berlin, which is part of the German federal environment agency (UBA). After spilling refined commercial products into an artificial channel, the aim of these experiments was to study the drift of the oil spill and the dissolution in the water column. Experimental results on situations with controlled conditions will allow the quality of the numerical predictions to be confirmed and validated.

International Journal of Environmental Science & Technology, 2010

Oil spills is one of the most important hazards in the estuarine and coastal water. In recent decades, engineers try to predict the status of oil slick to manage the pollution spreading. The prediction of oil slick transport is carried out mainly by means of numerical models. In the current study, the development and application of a two-phase fluid flow model to simulate oil transport in the marine environment are presented. Different transport and fate processes are included in the developed model. The model consists of the Lagrangian method for the advection process, the Random Walk technique for horizontal diffusion process and the empirical equations for the fate processes. The major forces for driving oil particles are fluid current, wind speed and turbulent flow. Therefore, the multi-component hydrocarbon method has been included to the developed model in order to predict fate processes. As prediction of particle velocity components is of major importance for oil slick advection, therefore the binomial interpolation procedure has been chosen for the particle velocity components computations. In addition, shoreline boundary condition is included in the developed model to simulate shore response to oil slick transport near the beaches. The results of the model applications are compared with the analytical solutions, experimental measurements and other numerical models cited in literature. Comparisons of different sets of results represent the capability of developed model to predict the oil slick transport. In addition, the developed model is tested for two oil spill cases in the Persian Gulf.

Journal of Geophysical Research: Oceans, 2017

Application of dispersants aims to enhance the natural dispersion process in order to reduce the size of the slick and the amount of oil at the surface. This study presents an approach for modeling the development of the surface oil slick as a function of the wind speed, oil viscosity, and dispersant application. We modeled the oil slick mass distribution across a transect through the slick over time taking into account the continuous entrainment of oil, resurfacing process of the different oil droplet size classes and horizontal transport. Outcomes show distinctively different oil slick features, depending on how favorable conditions are for dispersion. A large comet-shaped slick is formed in the case of suboptimal dispersion. Optimal dispersion yields a small surface oil slick, with a large mass of oil suspended. The benefit of dispersants is limited to in conditions with suboptimal natural dispersion, with the exception of extremely unfavorable conditions in which the slick size would be increased. The oil slick length, fraction of oil still floating, lifetime of the slick, and wind drift are highly influenced by wind speed and related mixing conditions, and to a lesser extent by oil properties. In the newly defined ''Dispersibility Factor'' (DF) the oil slick properties and environmental conditions can be combined into one value that correlates with the simulation outcomes and therefore can be used as an indicator of favorability of natural dispersion and likelihood of added value of chemical dispersion. Plain Language Summary In certain conditions, (part of) an oil spill can disappear from the water surface through a process called natural dispersion. One available oil spill response option is to enhance this process by addition of dispersants (chemical dispersion). An informed decision for such response requires insight in the oil slick size WITH and WITHOUT treatment. This paper aims to enable such assessment of net effectiveness, by providing a strategy for modeling the dispersion process. The findings of earlier laboratory investigations were applied in a model that simulates submergence of oil by breaking waves, rise of the separate oil droplets and concurrent wind-driven differential transport between the floating slick and suspended droplets. The simulation outputs help assess the added value (or not) of dispersant application in reducing the potential adverse effects of the surface oil slick for different oil types and conditions. not provide information on the added value of dispersants compared to only natural dispersion [National Research Council of the National Academies, 2005; Zeinstra-Helfrich et al., 2015]. Chemical dispersants can enhance the natural dispersion process by reducing the oil-water interfacial tension. This stimulates oil entrained by breaking waves to be broken up into smaller droplets. The droplet size affects the fate of the oil, as smaller droplets remain in the water column before resurfacing. Generally, droplets with sizes below 70 lm are considered to remain in the water column indefinitely [French-McCay, 2004]. Considering the random and chaotic processes that make up the dispersion process, such a sharp (and fixed) cutoff seems inappropriate.

An Integrated 2DH numerical model based on Eulerian approach including hydrodynamic, suspended sediment transport, oil transport and combined oil slick-sediment transport module has been developed and validated against laboratory measured values. FVM method and ADI (Alternating Direction Implicit) scheme have been employed for disceritization and solving governing equations. The second order Lax-Wendrof and second order central difference schemes have been used for advective and diffusive terms respectively. Multiphase oil spill model (MOSM) approach has been taken to simulate oil slick and flow interaction. All three modules of the numerical model have been validated against experimental data. The model capability for simulation, oil spill and suspended sediment transport, has been examined and the predictions show reasonable accuracy compared with analytical solutions and measured values reported in the literature. As an application the effect of oil in suspended sediment transport has been investigated for alternative concentrations which show increase of concentration of suspended sediment with the increase of oil entered in water column.

2017

The evolution of oil spilled in marine environments is affected by its spread, evaporation, emulsion, dissolution and dispersion in the water column. Although it has an environmental impact on marine ecosystems and affects determination of the spilled oil lifetime, vertical dispersion is of great importance; however, less attention has been paid to this complex phenomenon in comparison with other processes. This article is a critical review of the existing analytical relationships for oil dispersion calculation. The implementation of these formulae in numerical models is not straightforward. A comprehensive review of numerical oil dispersion models is presented with the advantages and disadvantages of each approach. In addition, experimental oil spill studies are reviewed and their obstacles are discussed. Analysis of experimental data cited in the literature has been carried out and variations in the oil concentration distribution in water bodies has been investigated. The current ...